Branching Out: The MeSH Vocabulary, Video Transcript

The U.S. National Library of Medicine is part of the National Institutes of Health in Bethesda, Maryland.

In 1960, NLM created the MeSH vocabulary.

MeSH stands for Medical Subject Headings.

The MeSH vocabulary is similar in concept to keywords on other systems. MeSH vocabulary includes four types of terms: Headings, Subheadings, Publication Types, and Supplementary Concept Records.

A MeSH heading represents a concept found in the biomedical literature. MeSH headings can be broad in scope, such as "Musculoskeletal System," or narrow in scope such as the heading, "Eyelashes."

The MeSH vocabulary is updated yearly. New MeSH headings are carefully selected for inclusion based on their importance to clinical care and research, and their significance and usage in the literature.

MeSH covers a variety of biomedical subjects as well as many non-clinical topics. These subjects make up different branches of what is known as the MeSH Tree Structure.

The tree has 16 main branches, or categories, including Anatomy, Organisms, Diseases, Chemicals and Drugs, Humanities, Health Care and Geographic Locations.

The MeSH tree structure is a hierarchy. Headings are positioned in the tree according to their relationship to other headings.

Look at the heading Eye in the Body Regions branch under Anatomy. Notice that the headings, Eyebrows and Eyelids are indented under "Eye" because these specific parts of the eye are narrower in scope. Also, see that the more specific heading, Eyelashes is indented quite logically under "Eyelids."

Many headings occur in more than one branch of the tree. Looking again at the heading, "Eye," we see that in addition to being in the Body Regions branch it is also found in the Sense Organs branch.

The National Library of Medicine produces MEDLINE, a database of citations to biomedical journal articles. MEDLINE is widely respected because the citations are enhanced with MeSH vocabulary terms. MEDLINE is the largest component of the PubMed system. PubMed users can use MeSH terms in their searches.

Subject specialists in anatomy, chemistry and other related fields are trained by NLM to become indexers for the National Library of Medicine’s MEDLINE database. Indexers, many of whom are language specialists, review journal articles and assign the most specific MeSH headings necessary to reflect the central concepts discussed in the articles. When there is no single specific MeSH heading for a concept, the indexer will use the closest, more general MeSH heading available. The indexer will assign as many MeSH headings, usually ten to fifteen, as appropriate to cover the topics of the article. This provides the searcher a variety of subject access points to each article.

An asterisk is used to indicate the MeSH concepts that are considered to be the main point of the article.

Indexers must also assign MeSH headings to describe the group or person being studied. These check tags as they are called specify human and animal studies, male and female studies, the age of the group or individual studied, and the type of the article being indexed.

The type of the article being indexed is noted using special MeSH headings called Publication Types. The Publication Type, "Journal article" is the most common item cited in MEDLINE. Other publication types including, Review, Clinical Trial, and Practice Guideline are popular for use in searching.

Subheadings are another type of specialized MeSH term. Subheadings can be used in combination with MeSH headings. There are over eighty Subheadings that can be used by indexers to further identify a particular aspect of a MeSH concept. For example, the subheading "Diagnosis" is used with MeSH terms for diseases when the article is about the diagnosis of that disease.

This article, about the diagnosis of autism, has been indexed with the MeSH heading "Autistic Disorder" and the subheading, "diagnosis." You can also use Subheadings in your searches to help make your retrieval very specific. For example, if you want to search for MEDLINE citations to articles about headaches, but specifically about treating headaches, you can search for the MeSH heading "Headache" and the subheading, "therapy."

Articles are indexed using the most specific MeSH headings available, and you should follow that same principle when selecting headings for your search. For example, if you were searching for articles about low level laser therapy, you should use the specific heading "low level laser therapy," not the more general heading, "Phototherapy."

In another example, to retrieve citations to articles about inflammation of the urinary bladder, use the heading "Cystitis," not the broader term, "Bladder Diseases."

The MeSH database can help you find MeSH terms and search with them in PubMed.Let’s use the MeSH database to look for the concept of Gastroparesis, a stomach disorder.

Here is the record in the MeSH database for this concept. The term used for the concept displays at the top.

A definition is often provided. If a term was added to the MeSH vocabulary after the early-1960s, the Year Introduced is displayed. This term was introduced in 1995.

In a minute we will see how this concept was indexed prior to that year.

Here are the subheadings that are found with the MeSH heading Gastroparesis on MEDLINE records. You can use the check boxes to select any that you want to use to focus your search. To see the definitions of the subheadings, follow this link.

You can select the option to search this term when it is the major topic of an article. That will help improve the relevancy of the retrieval.

Many MeSH headings have Entry Terms. Entry terms are considered to be synonymous, or close in scope to the MeSH term. PubMed recognizes these terms so that, if you search with an Entry Term, the appropriate MeSH term will be included in the search.

Let’s show this in PubMed. If we search for gastric stasis, PubMed will recognize this as an entry term for Gastroparesis and citations with that heading will be retrieved. This ability to use variant names for a concept allows invaluable flexibility for searchers.

Back in the MeSH database record for Gastroparesis…let’s look at the Previous Indexing for this concept. This tells us how articles on this topic may have been indexed prior to the year the term was introduced. Remember, this concept was introduced in 1995. Before that, the term Stomach Diseases was used to index this topic.

At the bottom of the record we see the position of this heading in the hierarchy. This term has been placed in two branches of the MeSH tree. This is the placement of the term in the Digestive System Diseases branch, and this is the placement of the term in the branch for Pathological Conditions, Signs and Symptoms. We can see broader terms, but there are no narrower terms under Gastroparesis.

Let’s use the MeSH Database to look for a MeSH heading to use in a search for light therapy.

A search for this term in the MeSH Database takes us to the record for the term, Phototherapy.

Here is a definition of the heading.

We see this concept was introduced in MeSH in 1981.

Here are the subheadings that appear with this heading in MEDLINE and are available for searching.

Notice the Entry Terms which include the term we used to search the database. Remember, any of these can be used to search PubMed for this MeSH concept.

Here is the MeSH tree representation that includes this term.

Notice that there are more specific headings indented under Phototherapy, including Color Therapy, Heliotherapy, and Ultraviolet Therapy.

When searching a broad term in PubMed, indented headings are included. This is known as the automatic explosion feature. In this example, a search of Phototherapy will retrieve citations for articles indexed with these more specific terms.

The term PUVA Therapy has a plus sign indicating that there are more specific terms indented under it. To see these terms, follow the link to go to the record for this term.

Scrolling down to the display of the hierarchy we see the indented term, Photopheresis. It does not have a plus sign, so there are no terms indented under it.

In addition to MeSH headings, Subheadings, and Publication Types, the MeSH vocabulary also includes approximately two hundred thousand Supplementary Concept Records that indexers also use to identify topics discussed in articles. The majority of these terms represent chemicals and substances that are mentioned in a significant way in an article.

As with other MeSH terms, Supplementary Concepts display on MEDLINE records and can be used by searchers.

New concepts continually appear in the published literature. Therefore, the MeSH vocabulary must be updated at regular intervals.

As you can see, the MeSH vocabulary is an important part of the National Library of Medicine’s mission to index the biomedical literature and to facilitate literature searching.